Polishing of a work such as a semiconductor wafer is performed by pressing in contact with a surface to be polished of the work to the surface of a polishing pad on a polishing plate to which the polishing pad is adhered, and by rotating the polishing plate while supplying a polishing liquid onto the polishing pad.
Then, after the completion of the polishing, polishing waste or the polishing liquid has infiltrated into the polishing pad to thereby lower a polishing rate, and thus, usually, high-pressure cleaning water is jetted to the polishing pad for each one batch of the polishing to thereby wash away the infiltrated polishing waste or the polishing liquid (Patent Literature 1). Furthermore, even when the polishing pad is cleaned for each one batch of the polishing, the polishing pad usually causes undulation (uneven surface) when performing polishing of as many as approximately seven batches, and a degree of flatness is lowered and a polishing rate is lowered.
Accordingly, a configuration is such that a carrier of a work is taken out from a polishing apparatus after performing polishing of approximately seven batches and instead, a ring-shaped correction grind stone provided with a gear is mounted and a dressing operation of grinding polishing pads of upper and lower polishing plates and of flattening the polishing pads is performed using the ring-shaped correction grind stone. Among four ring-shaped correction grind stones, the two correction grind stones are used for dressing the polishing pad of the lower polishing plate, and the other two ring-shaped correction grind stones are used for dressing the polishing pad of the upper polishing plate.
However, even when the polishing pad is cleaned by jetting high-pressure cleaning water for each one batch of polishing, an uneven surface is gradually generated in the polishing pad for each of batches, and the polishing rate of a work is lowered. In addition, although the polishing rate is restored by grinding and flattening the polishing pad through the use of a correction grind stone after polishing of seven batches, the polishing rate is not maintained constant and a degree of polishing is adjusted by polishing time, and thus there are problems in which the control is troublesome and accurate polishing is difficult to be performed. Furthermore, there is a problem in which the time of approximately 15 to 20 minutes on every occasion is required for replacing a carrier with a ring-shaped correction grind stone and of performing a dressing operation, after polishing of seven batches, and thus work efficiency is poor. Moreover, there is a problem in which a span of life of a polishing pad is also short since a dressing operation of grinding the polishing pad through the use of a correction grind stone every time after polishings of seven batches, is performed.
Accordingly, in Patent Literature 2, a configuration is such that, in place of a large ring-shaped correction grind stone, a small cuboid-shaped dressing grind stone is moved in the radial direction of upper and lower polishing plates at each completion of polishing of one batch and a dressing operation is performed on every occasion.
According to the method, there are advantages that, since a small dressing grind stone is used, the dressing grind stone can be moved in the radial direction by utilizing a gap between adjacent carriers and the dressing operation can be performed while the carrier is left mounted, and that, since the dressing operation is finely performed at each completion of polishing of one batch, the degree of flatness of the polishing pad can be maintained and thus highly accurate polishing can be performed.